In recent years, in solid-state imaging devices, a dynamic range of a pixel has been reduced as the number of pixels increases and the size of a pixel decreases. In the solid-state imaging devices, a portion of a subject having high brightness is likely to undergo saturation of output charges on a quantity of incident light. For example, measures of reducing an output gain or reducing a charge accumulation time may be taken on the saturation of the output charges. In this case, the saturation of the output charges can be reduced in a portion with high brightness, but it is difficult to obtain an appropriate output in a portion with low brightness.
A high dynamic range (HDR) synthesis is known as a photography technique for expressing a dynamic range larger than in normal photography. For example, as a HDR synthesis technique, there is a technique of causing a charge accumulation time or an output gain to differ according to a horizontal line formed by arranging pixels in a row in the horizontal direction. According to this technique, the resolution in the vertical direction practically decreases by half compared to the case of normal photography, and thus there is a problem in that the resolution is lowered.
Further, as another HDR synthesis technique, for example, there is a technique of synthesizing two or more images obtained by making charge accumulation times or output gains different from each other. According to this technique, a frame rate of a synthetic image is delayed compared to an output period of an image sensor. For this reason, particularly, when a moving picture is captured, there is a problem in that a blur (a motion blur) is likely to occur in a subject image. Further, since a frame memory used to synchronize frame timings of a plurality of images is necessary, the size of a circuit increases, and thus the cost increases, and the power consumption increases.